Pope Francis started a landmark, three-day visit to the United Arab Emirates on Sunday, becoming the first pontiff of the Roman Catholic Church to visit the Arabian Peninsula.

The visit offers a rare note of hope for Christians in the Middle East, who in recent decades have come under intense pressure in the region where their faith has its roots. Many have been persecuted, killed or forced to flee.

The pope’s presence in the Gulf — an area where religious freedom has traditionally been highly restricted — will shine a light on the broader role of Christianity in the Middle East. Before his plane took off, the pope also addressed the situation in Yemen, where a dire humanitarian crisis is unfolding — a pointed intervention because his Emirati hosts are among the war’s leading belligerents.

Christianity has been threatened, particularly in the Gulf.

Wars, jihadist violence and sectarian tensions have reduced the proportion of Christians in the Middle East to about 4 percent of the population today, from about 20 percent before World War I, according to the Vatican.

In ultraconservative Saudi Arabia, which has an estimated 1.4 million Christians, churches are banned and public display of Christian symbols is prohibited. Christians worship at underground services, or not at all.

In Yemen, which has a rich history of religious diversity, small Christian communities were established after missionaries arrived in the 19th century. But the conflict that has devastated Yemen since 2015, when Saudi Arabia sent troops to oust Houthi rebels, has forced many Christians into hiding.

Churches have been vandalized or burned to the ground, and many Christians fear persecution as religious extremists grow stronger on every side of the war.

Hundreds of thousands of Christians fled Iraq during the sectarian bloodshed that followed the American invasion in 2003, or were pushed out of northern Iraq and Syria as the Islamic State spread across the region starting in 2014 and imposed an extreme form of Islam on local populations.

In Egypt, where Christians account for about 10 percent of the country’s 98 million people, Islamic State militants have bombed churches and gunned down Christian pilgrims on their way to remote desert monasteries.

Pope Francis has warned that Christians could eventually disappear from the region altogether amid “murderous indifference” to their plight.

Why the United Arab Emirates, and why now?

The Gulf countries, which include the United Arab Emirates, are among the few in the Middle East where Christian numbers are rising, despite their history of restricting religious freedom.

An influx of migrant workers from the Philippines, India and other Asian countries has brought several million Christians to countries like Saudi Arabia, the United Arab Emirates and Qatar, though their ability to worship varies greatly.

In the United Arab Emirates, Christians, Hindus and Jews can worship openly.

Crown Prince Mohamed bin Zayed al-Nahyan of Abu Dhabi, one of the country’s seven emirates, invited the pope to visit after they met in the Vatican in 2016. His government’s Ministry of Tolerance has hosted events for Christian leaders, including one in 2017 at the site of an early Christian monastery on an Abu Dhabi island.

The United Arab Emirates is home to more than one million Christians, according to the Pew Research Center, about 13 percent of the population. Many are immigrants.

Pope Francis has called the country a “land that tries to be a model of coexistence” and began a video message about the trip last week with the Arabic salutation “Salaam alaikum” (“Peace be with you”).

“I am happy for this occasion the Lord has given me to write, on your dear land, a new page in the history of relations between religions,” he said in the video.

He added, “Faith in God unites and does not divide, it draws us closer despite differences, it distances us from hostilities and aversion.”

Though rulers in the United Arab Emirates have called 2019 the “Year of Tolerance,” the country restricts freedom of religion in significant ways. Conversion to Islam is promoted, while conversion from Islam to another religion is illegal. Blasphemy and apostasy still carry potential death sentences.

What is Pope Francis trying to achieve?

In January, Francis told ambassadors to the Holy See that his visit to the United Arab Emirates and a subsequent trip to Morocco in March were opportunities to improve understanding and relations between the faiths.

The theme of the pope’s visit comes from the opening words of the Prayer of St. Francis, his namesake: “Make me a channel of your peace.”

One of the pope’s main goals in his visit, church officials said, is to continue working with Muslim leaders in the hopes of making the Middle East and the Muslim world safer and more hospitable for Christians. In some ways, his message is aimed beyond the United Arab Emirates at countries like Saudi Arabia and Iran.

But a major part of his trip to the United Arab Emirates is also visiting the country’s vibrant Catholic community of foreign workers, and another of the pope’s goals is to encourage and support them in this peripheral part of the church.

The pope also made a public appeal on Sunday for the end of Yemen’s humanitarian crisis, fueled by a war that has pushed millions to the brink of starvation. Making his regular address in St. Peter’s Square, he urged all sides to respect international agreements and to ensure food reached suffering Yemenis.

The United Arab Emirates is Saudi Arabia’s main military partner in its war against Iranian-aligned Houthi rebels in Yemen, which is supported by the United States.

A version of this article appears in print on , on Page A7 of the New York edition with the headline: Why the Pontiff’s Journey To the Mideast Matters. Order Reprints | Today’s Paper | Subscribe